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In this paper we study some variants of Dirac-type problems in hypergraphs. First, we show that for $k\ge 3$, if $H$ is a $k$-graph on $n\in k\mathbb N$ vertices with independence number at most $n/p$ and minimum codegree at least…

Combinatorics · Mathematics 2018-02-20 Jie Han

In this paper we prove an asymptotic multipartite version of a well-known theorem of K\"uhn and Osthus by establishing, for any graph $H$ with chromatic number $r$, the asymptotic multipartite minimum degree threshold which ensures that a…

Combinatorics · Mathematics 2017-07-17 Ryan R. Martin , Richard Mycroft , Jozef Skokan

Let H be any graph. We determine (up to an additive constant) the minimum degree of a graph G which ensures that G has a perfect H-packing (also called an H-factor). More precisely, let delta(H,n) denote the smallest integer t such that…

Combinatorics · Mathematics 2008-02-01 Daniela Kühn , Deryk Osthus

The study of asymptotic minimum degree thresholds that force matchings and tilings in hypergraphs is a lively area of research in combinatorics. A key breakthrough in this area was a result of H\`{a}n, Person and Schacht who proved that the…

Combinatorics · Mathematics 2023-09-01 Candida Bowtell , Joseph Hyde

Given a labeled graph $H$ with vertex set $\{1, 2,\ldots,n\}$, the ordered Ramsey number $r_<(H)$ is the minimum $N$ such that every two-coloring of the edges of the complete graph on $\{1, 2, \ldots,N\}$ contains a copy of $H$ with…

Combinatorics · Mathematics 2016-04-27 David Conlon , Jacob Fox , Choongbum Lee , Benny Sudakov

Bipartite graph tiling was studied by Zhao who gave the best possible minimum degree conditions for a balanced bipartite graph on 2ms vertices to contain m vertex disjoint copies of K_{s,s}. Let s<t be fixed positive integers. Hladk\'y and…

Combinatorics · Mathematics 2015-03-19 Andrzej Czygrinow , Louis DeBiasio

In this thesis we consider ordered graphs (that is, graphs with a fixed linear ordering on their vertices). We summarize and further investigations on the number of edges an ordered graph may have while avoiding a fixed forbidden ordered…

Discrete Mathematics · Computer Science 2009-07-16 Craig Weidert

Drawing a graph in the plane with as few crossings as possible is one of the central problems in graph drawing and computational geometry. Another option is to remove the smallest number of vertices or edges such that the remaining graph…

Computational Geometry · Computer Science 2024-04-16 Akanksha Agrawal , Sergio Cabello , Michael Kaufmann , Saket Saurabh , Roohani Sharma , Yushi Uno , Alexander Wolff

In this paper, we introduce tiled graphs as models of learning and maturing processes. We show how tiled graphs can combine graphs of learning spaces or antimatroids (partial hypercubes) and maturity models (total orders) to yield models of…

Discrete Mathematics · Computer Science 2024-03-05 Špela Kajzer , Alexander Dobler , Janja Jerebic , Martin Nöllenburg , Joachim Orthaber , Drago Bokal

A tessellation of a graph is a partition of its vertices into vertex disjoint cliques. A tessellation cover of a graph is a set of tessellations that covers all of its edges. The $t$-tessellability problem aims to decide whether there is a…

Discrete Mathematics · Computer Science 2021-06-24 A. Abreu , L. Cunha , T. Fernandes , C. de Figueiredo , L. Kowada , F. Marquezino , D. Posner , R. Portugal

In this paper we initiate a systematic study of the Tur\'an problem for edge-ordered graphs. A simple graph is called $\textit{edge-ordered}$, if its edges are linearly ordered. An isomorphism between edge-ordered graphs must respect the…

The degree/diameter problem for mixed graphs asks for the largest possible order of a mixed graph with given diameter and degree parameters. Similarly the \emph{degree/geodecity} problem concerns the smallest order of a $k$-geodetic mixed…

Combinatorics · Mathematics 2021-08-13 James Tuite , Grahame Erskine

Given graphs H_1,...,H_k, we study the minimum order of a graph G such that for each i, the induced copies of H_i in G cover V(G). We prove a general upper bound of twice the sum of the numbers m_i, where m_i is one less than the order of…

Combinatorics · Mathematics 2007-05-23 Zoltan Furedi , Dhruv Mubayi , Douglas B. West

The treewidth of a graph is an important invariant in structural and algorithmic graph theory. This paper studies the treewidth of line graphs. We show that determining the treewidth of the line graph of a graph $G$ is equivalent to…

Combinatorics · Mathematics 2014-09-25 Daniel J. Harvey , David R. Wood

Given a graph $H$, a perfect $H$-factor in a graph $G$ is a collection of vertex-disjoint copies of $H$ spanning $G$. K\"uhn and Osthus showed that the minimum degree threshold for a graph $G$ to contain a perfect $H$-factor is either given…

Combinatorics · Mathematics 2023-02-28 Domagoj Bradač , Micha Christoph , Lior Gishboliner

Given $3 \leq k \leq s$, we say that a $k$-uniform hypergraph $C^k_s$ is a tight cycle on $s$ vertices if there is a cyclic ordering of the vertices of $C^k_s$ such that every $k$ consecutive vertices under this ordering form an edge. We…

Combinatorics · Mathematics 2021-07-01 Jie Han , Allan Lo , Nicolás Sanhueza-Matamala

Let $G$ and $H$ be $k$-graphs ($k$-uniform hypergraphs); then a perfect $H$-packing in $G$ is a collection of vertex-disjoint copies of $H$ in $G$ which together cover every vertex of $G$. For any fixed $H$ let $\delta(H, n)$ be the minimum…

Combinatorics · Mathematics 2015-09-16 Richard Mycroft

We introduce a counterpart to the notion of vertex disjoint tilings by copy of a fixed graph F to the setting of graphons. The case F=K_2 gives the notion of matchings in graphons. We give a transference statement that allows us to switch…

Combinatorics · Mathematics 2021-01-05 Jan Hladky , Ping Hu , Diana Piguet

Boettcher, Schacht and Taraz gave a condition on the minimum degree of a graph G on n vertices that ensures G contains every r-chromatic graph H on n vertices of bounded degree and of bandwidth o(n), thereby proving a conjecture of Bollobas…

Combinatorics · Mathematics 2012-09-06 Fiachra Knox , Andrew Treglown

An ordered graph $G$ is a graph together with a specified linear ordering on the vertices, and its interval chromatic number is the minimum number of independent sets consisting of consecutive vertices that are needed to partition the…

Combinatorics · Mathematics 2021-02-18 Dana Neidinger , Douglas B. West